Regulator for electrically-actuated air-compressors.



No. 664,086 Patented D80. 18, I900.

E. 'm. HEWLETT.

REGULATOR FOR ELEGTRIGALLY ACTUATED AIR GOMPRESSORS. (Application filedNov. 7, 1898.)

(No Model.)

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UNITED STATES PATENT Orrics.

EDWARD M. HEWLFTT, OF SCHENECTADY, NEXV YORK, ASSIGNOR TO THE GENERALELECTRIC COMPANY, OF NEIV YORK.

REGULATOR FOR ELECTRICALLY-ACTUATED AlR-COMPRESSORS.

SPECIFICATION forming part of Letters Patent No. 664.086, dated December18, 1900.

Application filed November '7, 1898. Serial No. 695,669. (No model.)

To aZZ whom it may concern:

Be it known that I, EDWARD M. HEWLETT, a citizen of the United States,residing at Schenectady, in the county of Schenectady and State of NewYork, have invented certain new and useful Improvements in Regulatorsfor Electrically- Operated Air- Compressors, (Case No. 632,) of whichthe following is a specification.

My invention relates to electrically-operated aircompressors or similarmachines in which fluid is pumped into a reservoir until a certainpressure is reached, at which time the operation of the electric motoris interrupted, usually by opening its circuit. These devices havemaximum and minimum operating positions, the motor being thrown intoaction in the lower position or when the pressure reaches a certaindeterminate lower limit and its action being suspended when the upperlimit is reached. Several different types have been devised, the problemof starting and stopping these devices being quite a different one fromthose involved in the use of other motive powers. One type with which Iam familiar might be called an air-relay devicethat is, a small valve isactuated by the regulator and by its operation works a larger valve,which in turn admits the full pressure to actuate a switch of one formor another. The general type has been unsatisfactory because of theleakage in the air apparatus and because of the difficulty in keeping itin order and its general complication. There have been other typesinvolving their own difficulties, to which it is unnecessary to refer.Some, at least, of these difficulties are overcome by the apparatus ofmy invention, which has in practice operated successfully. It consistsin general in the form herein illustrated of a spring with a switchattached thereto, the switch having two positions of contact, in one ofwhich, corresponding to the inferior pressure limit, it closes thecircuit of the motor through a magnet-coil in the seriescircuit. Themagnet-coil operates a shunting-contact through which the main currentis delivered to the motor, the operation of the device being thus toshunt the starting-contact practically immediately after it has startingof the series-relay magnet, as I prefer to call it, and is carriedthrough the magnetcoil in opposite directions, so that the two parts ofthe coil act differentially and the magnet-core is deenergized. Asuitable spring then opens the main circuit of the motor. I also preferto provide a blow-outmagnet for the main contacts, so that they may notbe subjected to any damage from arcing. It is manifest that thisarrangement differs from many preceding devices in that no attempt ismade to use a shunt-coil. The motors which are commonly employed in thiswork are five-hundred-volt machines, since these devices areparticularly useful in rail way-work and the winding of the shunt-coilfor such potentials is expensive and the coil itself is liable toaccident. I therefore avoid the difficulty by using the series coil inthe way pointed out and avoid the difficulty of the large currentrequired to start the motor by the relay action which I have alreadydescribed in brief and which will be better un; derstood from theaccompanying specification.

The scope of my invention will be pointed out in the attached claims.

The drawings show an apparatus embodying myinvention particularlyadapted for furnishing the compressed air to operate an airbrake system.

Figure 1 is a front elevation; Fig. 2, a section on the line 2 2 of Fig.1, showing some of the parts in side elevation; and Fig. 3 is a diagramof the circuits.

In the drawings, A is the frame of the ap- 9o interposed and is held inplace by the screws B. A spring E is provided, and a plate D at the baseof the spring reciprocates under the variations of pressure in such away as to com- 100 K series-relay coil already referred to.

press the spring as the pressure rises, the upper limit of the platesmotion being determined by the shoulder (Z on the case of the boxcontaining the spring. A second plate D at the top of the spring is heldin place by the screws 1) D by the adjustment of which the tension ofthe spring may be regulated. A core F, passing through the spring, isfastened to the plate D and is pivoted atf to an arm G. This arm ispivoted at g to a suitable part of the frame and carries a piece ofinsulation g, in which is set a strip of metal carrying the contact G,which reciprocates between the upper and lower contacts H H. Thesecontacts are preferably of carbon, while the contact G is of metal, sothat there will be no difficulty from arcing. In practice, as will bepointed out farther on, the circuit is not opened at these contacts insuch a way as to cause any serious tendency to are.

M is the armature of a coil 1, which is the The armature M carries apair of contacts K K, which are connected by a bar K and are secured tothe piece of insulation M. A spring an opposes the motion of thearmature. The contacts K K and the bar K bridge the contacts K K in theseries circuit. A blow-out-magnet coilI energizes the pole-piece P, themagnetic circuit being so arranged as to blow the arcs out at the sidesof the apparatus through suitable chutes L L, provided for this purpose,which chutes act to restrain the are and prevent damage to the metallicportions of the apparatus. The chutes, as is well understood, should beformed of some refractory insulating material, such as compressed fiber.

The circuits of the apparatus will be best understood from Fig. 3. Inthis figure, N is the motor, 0 is the compressor operated by the motor,P is the main reservoir, and P is the train-pipe, from which leads thepipe 0 to the apparatus A, already described. In the illustratedposition the motor is just starting.

Current enters from the trolley T and passes to the lower contact H, thecircuit of the upper contact H being open at this time. From here itpasses to the contact G, through the magnet-coil l, and by the leaddirectly to the motor N. As the current thus passes through the coil 1,the armature M is attracted and closes the circuit of the contacts K K.The current then passes by these con tacts through the blow-out-magnetcoil 1 and through part only of the coil 1 to the contact H, and thusdirectly to the motor, a part of the coil being sufficient to hold thearmature attracted after the entire winding has overcome the increasedreluctance due to the wide air-gaps when the armature is in the positionshown in dotted lines. The contact G, assuming that it still remainstouching the contact H, is thus practically short circuited, so thatonly a very small amount of current will pass through it, and it will beseen that the passage through it of the starting current to the motor,which,

if continuous or enduring for any length of time, would be destructive,is attended with no risk. This is the operation at starting. Itmanifestly occurs as soon as the contact G touches the contact H. When,however, the superior limit of pressure is approximated, the contact Grises until it touches the contact 1-1. It will be seen, as alreadyindicated, that as the contact G moves from the contact H there ispractically no current in its circuit, the armature M having shunted thecurrent across the contacts K K, so that practically no are forms. Whenthe contact G touches the contact H, a new circuit is established, thetwo halves of the coil I being now thrown in multiple and the currentpassing through them in opposite directions, so that the magnet iskilled and the spring on (see Fig. 2) opens the circuit of the contactsK K by withdrawing the armature M. The circuit of the trolley is thusopened and the blow-out magnet 1 takes care of the are at thesecontacts, which, it will be seen, have a considerable range of movement.The contacts K have a wiping motion over the contacts K, so that theyare kept clean and free.

In practice the apparatus has been found to operate successfully and toavoid the difficulties experienced with other devices with which I amacquainted. It is simple, substantial, and of moderate cost, there beingno complication of circuits, and the expensive and unreliable shunt-coilis avoided in its construction.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is-

1. In a fluid-pressLire-operated controller for an electric motor, thecombination of a switch having two circuit-closing positions, means forcausing the switch to assume one or the other position when the pressurereaches its superior and inferior limits, respectively, means forshunting the switch by a circuit of low resistance when in one position,and means for opening the shunt when the switch reaches the secondposition.

2. The combination in a regulator for an electrically actuated air pump,of a diaphragm actuated by the air-pressure against an opposing force, aswitch the position of which is determined by the resultant of the twoopposing forces, contacts for the switch corresponding respectively tothe opening and closing of the motor-circuit, a relay in circuit withthe motor-closing contact of the switch, and a shunt around the switchoperated by the relay.

The combination in a regulator for an electrically actuated air pump, ofa diaphragm actuated by the air-pressure against a spring, a switch theposition of which is determined by the resultant of the two opposingforces, contacts for the switch correspond ing respectively to theopening and closing of the motor-circuit, a relay in circuit with themotor-closing contact of th switch, and connections operated by theother contact of the switch fordeenergizing the relay-magnet and openingthe circuit.

4. The ml 'nation of a switch of moderate or small capacity with a shuntof large current capacity around its terminals, a contact correspondingto the inferior-pressure limit of a fluid-pressure system, which closesthe motor-circuit through the switch, a relay device operated by theclosing of the circuit for closing the shunt, a pressure-responsivedevice for opening the circuit at the switch as the pressure rises, thusleaving the shunt the only path to the motor, and meansin circuit withthe other point of the switch corresponding to the superior-pressurelimit, for opening the shunt when the switch makes the latter contact.

5. The combination of a two-point switch, an electromagnet'in circuitwith one point of the switch, a shunt around the switch opened andclosed by the action of the electromagnet, a lead from one of thecontacts of the shunt to an intermediate point of theelectromagnet-winding, and leads from the other point of the switch andits moving contact to the ends of the electromagnet-winding; wherebywhen the switch touches one point, a shunt is closed around its owncontacts by the action of the magnet, and when it touches the otherpoint, the magnet-coil acts differentially to deenergize the magnet andopen the circuit.

6. In a controlling device for an electric motor driving an air-pump,the combination of a switch, a pressure-responsive device actuating theswitch, a coil in series with the cont-act touched by the switch at theinferior limit of pressure, an armature operated by the coil, andcontacts on the armature for shunting the switch as soon as currentpasses.

7. An antisparking device fora switch, comprising a shunt-circuit aroundthe switch-contacts controlled by a coil in series with the contacts,said shunt-circuit including an armature controlled by said coil,sparloabsorbing contacts controlled by the armature, and means forholding said contacts closed until the switch-contacts have beenruptured, whereby the spark is absorbed by the auxiliary contacts.

3. The combination with a two-point switch, of a shunt in parallel toits movable and one of its fixed contacts, said shunt includingauxiliary contacts of large current-carrying capacity, a coilcontrolling the closure of the shunt when the circuit is completedthrough the switch-contacts, and means for demagnetizing said coil whenthe movable switch-contact engages the other fixed contact.

9. As a means for starting an electric motor, the combination of aswitch in the motorcircuit, a path of greater current capacity shuntingthe switch, and a quickly-responsive device operated by the completionof the m otor-circuit for closing the shunt as soon as the switchcloses.

10. The combination of a switch of moderate or small size, with a shuntof large capacity around its terminals, and an electromagnet in theswitch-circuit provided with a quickly-responsive armature for closingthe shunt when the switch-contacts touch.

11. The combination of a two-pointswitch, a normally open shunt aroundthe switch bridging its contacts, an electromagnet for closing the shuntactuated on closing the switch at one of its contacts, and means foropening the circuit when the switch engages its other contact.

12. The combination of a two-point switch, a shunt around the switchbridging its contact-s, an electromagnet in circuit with one point ofthe switch for closing the shunt, and means for passing current throughthe magnet-coil differentially when the switch touches the other point,thus opening the circuit.

13. In an electric switch mechanism, a contact operated by variations influid-pressure to close a circuit, a coil energized by said circuit, anda main switch controlling said coil.

14:. In an electric switch mechanism, a contact operated by variationsin fluid-pressure to close a circuit, a coil energized by said circuit,a main switch controlling said coil and in shunt to the contact, andmeans for deenergizing said coil responsive to variations in thetiuid-pressure.

15. In an electric switch mechanism, a contact operated by variations influid-pressure to close a circuit, a coil energized by said circuit, amain switch controlled by said coil (and in shunt to the contact), andmeans for deenergizing said coil responsive to variations in theiiuid-pressu re, and a blow-out magnet for the switch.

In witness whereof I have hereunto set my hand this 5th day of November,1898.

ED WVARD M. HEWVLETT.

Witnesses:

B. B. HULL, M. H. EMERSON.

